Will circular runways ever take off?

Hmm...interesting idea. first blush thoughts:

headwind changes to a crosswind, changes to a tailwind as you land/take-off?

banked runway means lateral load on the aircraft changes as speed increases, meaning you are slipping or crabbing on the ground?

turning take-off requires higher AOA to produce higher lift in turn? more chance of stall?

Americans don't know haw to drive in a round-about!

the real reason it won't work: drinks slide off the table in 1st class as you taxi to the "threshold".

On Friday, March 17, 2017 at 12:16:31 AM UTC+3, Matt Herron Jr. wrote:
Hmm...interesting idea. first blush thoughts:

headwind changes to a crosswind, changes to a tailwind as you land/take-off?

banked runway means lateral load on the aircraft changes as speed increases, meaning you are slipping or crabbing on the ground?

Smoothly increasing bank on the runway so you can start on flat ground at the start of the takeoff and go up the sides as the speed increases, keeping crab at zero.

turning take-off requires higher AOA to produce higher lift in turn? more chance of stall?

Not a lot.

At his suggested size of 3.5 km diameter, total G loading at 250 km/h would be 1.04 G, requiring a 2% higher takeoff speed and a 16 degree banking to be balanced.

At 2 km diameter those figures would be 1.12 G, 6% higher takeoff speed, and 27 degrees of bank.

At a very sporting 1 km diameter the figures would be 1.4 G, 20% higher takeoff speed, and 45 degrees banking.

OK, those all assume a constant 250 km/h, so actually it would be worse than that once you allow for the extra loading of the higher speed.

The suggested 3.5 km diameter is certainly very mild! Just almost impossible to find a site for.

On Friday, March 17, 2017 at 12:44:54 AM UTC+3, Bruce Hoult wrote:
On Friday, March 17, 2017 at 12:16:31 AM UTC+3, Matt Herron Jr. wrote:
Hmm...interesting idea. first blush thoughts:

headwind changes to a crosswind, changes to a tailwind as you land/take-off?

banked runway means lateral load on the aircraft changes as speed increases, meaning you are slipping or crabbing on the ground?

Smoothly increasing bank on the runway so you can start on flat ground at the start of the takeoff and go up the sides as the speed increases, keeping crab at zero.

turning take-off requires higher AOA to produce higher lift in turn? more chance of stall?

Not a lot.

At his suggested size of 3.5 km diameter, total G loading at 250 km/h would be 1.04 G, requiring a 2% higher takeoff speed and a 16 degree banking to be balanced.

At 2 km diameter those figures would be 1.12 G, 6% higher takeoff speed, and 27 degrees of bank.

At a very sporting 1 km diameter the figures would be 1.4 G, 20% higher takeoff speed, and 45 degrees banking.

OK, those all assume a constant 250 km/h, so actually it would be worse than that once you allow for the extra loading of the higher speed.

The suggested 3.5 km diameter is certainly very mild! Just almost impossible to find a site for.

Updated figures, allowing for increased takeoff speed feeding back into G loading and required bank angle..

Assumed straight runway takeoff speed 70 m/s, 252 km/h, 136 knots, 156.5 mph

3500 m diameter, 257 km/h, 1.044 G, 16.6 deg bank
2000 m diameter, 271 km/h, 1.155 G, 30.0 deg bank
1609 m diameter, 285 km/h, 1.276 G, 38.4 deg bank
1414 m diameter, 300 km/h, 1.414 G, 45.0 deg bank
1155 m diameter, 356 km/h, 2.000 G, 60.0 deg bank

The figures head to infinite speed and G at 1000 m diameter.